How would you prepare 500 mL of a 0.330 M solution of CaCl2 from solid CaCl2? Specify the glassware that should be used.

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Determine the molar mass of CaCl_2 by adding the atomic masses of calcium (Ca) and chlorine (Cl) from the periodic table.

Calculate the number of moles of CaCl_2 needed using the formula: \( \text{moles} = \text{molarity} \times \text{volume in liters} \).

Convert the volume from milliliters to liters by dividing by 1000.

Calculate the mass of CaCl_2 required using the formula: \( \text{mass} = \text{moles} \times \text{molar mass} \).

Use a balance to weigh the calculated mass of solid CaCl_2, dissolve it in a beaker with less than 500 mL of distilled water, then transfer the solution to a 500 mL volumetric flask and fill to the mark with distilled water.

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주요 개념

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Molarity

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. To prepare a solution, one must calculate the required amount of solute based on the desired molarity and volume. In this case, a 0.330 M solution means there are 0.330 moles of CaCl2 in every liter of solution, so for 500 mL, the calculation involves determining the moles needed and converting that to grams using the molar mass of CaCl2.

Preparation of Solutions

Preparing a solution involves accurately measuring the solute and diluting it to the desired volume. For a 0.330 M CaCl2 solution, one would weigh the calculated mass of solid CaCl2, dissolve it in a small volume of distilled water, and then transfer the solution to a volumetric flask to make up to the final volume of 500 mL. This ensures uniform concentration throughout the solution.

Glassware for Solution Preparation

The choice of glassware is crucial for accurate solution preparation. A volumetric flask is ideal for preparing solutions because it allows for precise measurement of the final volume. Additionally, a balance is needed to weigh the solid CaCl2 accurately, and a beaker or stirring rod may be used for dissolving the solute before transferring it to the volumetric flask.